Ulna

The ulna is the forearm bone on the little-finger side. It forms the elbow hinge with the humerus and articulates with the radius at both ends.

Proximal radioulnar joint: The pivot joint where the radial head rotates within the ulna’s radial notch. This articulation lets the radius rotate beside the ulna during forearm movement.
Forearm: The upper-limb region between the elbow and wrist, containing the radius and ulna. The ulna is one of the forearm’s two long bones.
Ulnar fracture: A break in the ulna, occurring alone or alongside injury to the radius or elbow. The ulna can fracture directly after blows or as part of forearm injury patterns.
Radius: The forearm bone on the thumb side, articulating with the ulna and wrist bones. Unlike the ulna, the radius directly meets most carpal bones and moves substantially during forearm rotation.
Distal radioulnar joint: The pivot joint between the head of the ulna and the ulnar notch of the radius. At the wrist end, the ulna participates in the rotation that turns the palm.
Humerus: The upper-arm bone that meets the radius and ulna at the elbow. Its trochlea articulates directly with the ulna at the elbow.
Monteggia fracture: A proximal ulna fracture accompanied by dislocation of the radial head. This injury combines a shaft fracture of the ulna with disruption at the elbow.
Fibula: The smaller lateral bone of the lower leg, paired with the tibia. Like the ulna, it is the less weight-bearing member of a paired limb-bone arrangement, but lies in the leg.
Olecranon: The large proximal projection of the ulna that forms the point of the elbow. It fits into the humerus during elbow extension and anchors the triceps tendon.
Carpal bones: The eight small bones forming the wrist between the forearm and hand. The ulna’s distal end is separated from the carpal bones by an articular disc.

Linked from 6 pages